Which enzyme is primarily responsible for the phosphorylation of glucose in the CK assay?

The enzyme that plays a crucial role in the phosphorylation of glucose in the clinical setting of the creatine kinase (CK) assay is hexokinase. This enzyme catalyzes the conversion of glucose to glucose-6-phosphate by utilizing ATP as a phosphate donor, which is an essential step in glucose metabolism and is often used to measure glucose levels in biological samples.

Hexokinase is favored in this context because it has a high affinity for glucose and can function well at the lower concentrations typically present in biological fluids. This reaction is essential not only for energy production but also for the subsequent pathways of glucose utilization and storage. The accurate measurement of glucose levels using hexokinase is particularly important due to its relevance in diagnosing metabolic conditions, including diabetes.

Other enzymes mentioned, such as adenylate kinase, pyruvate kinase, and lactate dehydrogenase, are involved in different metabolic pathways and do not phosphorylate glucose directly. Instead, they participate in energy transfer and conversion processes, which are not central to the specificity required in the CK assay. Thus, hexokinase is the enzyme that is directly involved in the phosphorylation step necessary for the assessment of glucose in this context.